1. Technical Field
The present invention relates to a power supply unit using a printed circuit board accommodated in a housing which is provided with a cooling member.
2. Related Art
Switching power supply units are well known. For example, JP-A-2002-345245 discloses an example of a technique related to a switching power supply unit. This switching power supply unit is able to increase packaging density of components, easily reduce size, reduce resistance loss at terminal connecting portions and enhance power supply efficiency. Also, in this switching power supply unit, a transformer, lead portions, electrode members and the like are fixed to one designated surface of a given circuit board. The lead portions, which correspond to portions of extended flat metal windings, have ends connected to the electrode members.
Further, for example, JP-A-2004-297887 discloses an example of a technique related to a water-cooled switching power supply with a reduced size. This switching power supply includes a base plate on which a switching circuit, main transformer, rectifier circuit and smoothing circuit are mounted. The base plate is also provided thereon with a seat member, in which a coolant passage is formed to cool electronic components. A control circuit board for controlling the switching circuit is arranged above the base plate (see JP-A-2004-297887). Although not shown in JP-A-2004-297887, the switching power supply also includes circuit elements for controlling the switching circuit. The circuit elements have no other alternative but to be mounted on the upper surface of the control circuit board. This is because the upper surface of the base plate (i.e. beneath the control circuit board) is used for mounting the switching circuit, the main transformer and the like.
Accordingly, it is difficult to ensure a space for mounting the circuit elements for the control circuit board on the upper surface of the base plate. In the event the circuit elements are mounted on the upper surface of the base plate, the circuit elements are limited to those which have a small height when mounted.
Combination of the techniques disclosed in JP-A-2002-345245 and JP-A-2004-297887 can provide the following technique. In the technique disclosed in JP-A-2002-345245, the lead portions and the elements or parts, such as the electrode members, are arranged on one designated surface. On the other hand, in the technique disclosed in JP-A-2004-297887, the switching elements are required to be cooled by the seat member formed on the base plate. Therefore, the switching elements are inevitably arranged on the other side of the circuit board (the side opposite to the surface on which the elements or parts are arranged). An example of this arrangement is illustrated in FIG. 1.
As shown in FIG. 1, different-shape components (Pa, Pb, Pc, Pd, Pe, etc.), such as circuit elements or parts, are mounted on a circuit board (BP). In the figure, the dimension of the components in a height direction is indicated by Hb relative to the mounting surface of the circuit board (hereinafter referred to as a mounted height). When the entirety, including the different-shape components, the switching circuit and the like on the base plate, the cooling member, and the like, is to be accommodated in a housing, the housing is required to ensure a space (height) larger than a height Ha (Ha>Hb), leading to the necessity of increasing the size. On the other hand, a gap formed between the circuit board and the base plate and having a height He may allow arrangement such as of the circuit elements or parts.
However, an attempt of reducing the size of the housing raises a problem that the circuit elements or parts arranged in the gap are limited to those which have a small mounted height. On the other hand, arranging the circuit elements or parts having a large mounted height in the gap raises a problem of easily producing a dead space because not all the circuit elements or parts have an even mounted height.